Kilbroney River ASSI

Kilbroney River is a special place because of its earth science interest. The area provides access to important rocks in the Western Mournes area.

The rocks are igneous, that is they formed from molten magma deep beneath the Earth’s crust. They date from the Palaeogene period of Earth’s history and are some 56 million years old.

The Western Mournes are slightly younger in age than the Eastern Mournes, and are mostly made up of two types of granite.

These granites made their way into the crust as a sequence of separate events over time, so the first ones had become solid before the next ones appeared. This means that usually where two granites meet, they are sharply separated and it is easy to tell them apart.

At Kilbroney River, however, the later granite was able to melt it’s way into the older granite so they are not so distinctly separated, with patches of the older rock found in the younger one. These patches actually show different amounts of melting.

This is important because Kilbroney River is the only place you can see this special type of relationship in the Western Mournes area.